The present invention relates generally to fluid pressure switches.
Tire pressure sensors are standard equipment on many vehicles manufactured today. The tire pressure sensors can alert drivers when the tire air pressure becomes dangerously low and avert the likelihood of an accident caused by low tire pressure.
Typical pressure measurement sensors use a piezo-resistive silicon-based pressure sensing element for measuring fluid pressure. Unfortunately, these sensors can consume a considerable amount of current from sources used to power them. For some applications, e.g., tire pressure sensing, a very small battery is used as the power source and the life of the battery is a very important design factor. As recognized herein, by using a pressure activated switch, the sensor circuitry can be modified to minimize the amount of current required to operate the sensor and thus, reduce the electronic overhead of the sensor. With fewer required components, manufacturing costs are reduced.
It happens that fluid pressure activated switches are available. However, since these switches only include a single trip point and are actuated at only a single pressure value, a single fluid pressure activated switch cannot be used to report multiple pressure values in a system.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A multiple contact fluid pressure switch includes a plate. A rib extends from the plate to establish a cavity on the plate. Two lower contacts are installed in the cavity. A diaphragm encloses the cavity. An upper contact is disposed on the diaphragm. The multiple contact fluid pressure switch is movable between an open position wherein the upper contact does not engage the lower contacts, a first closed position wherein the upper contact engages only one lower contact, and a second closed position wherein the upper contact engages both lower contacts. In a preferred embodiment, the diaphragm is disposed on the rib.
In one aspect of the present invention, a central rib extends from the plate and divides the cavity into a first cavity and a second cavity. A first lower contact is disposed within the first cavity and a second lower contact is disposed within the second cavity. Moreover, the diaphragm is a first diaphragm that encloses the first cavity and the second cavity, and the switch further includes a second diaphragm that is affixed to the first diaphragm. The second diaphragm spans the area above the second cavity. In this aspect of the present invention, the switch includes a first upper contact that is affixed to the first diaphragm above the first lower contact and a second upper contact that is affixed to the first diaphragm above the second lower contact. The switch is movable between an open position wherein the upper contacts do not engage the lower contacts, a first closed position wherein the first upper contact engages the first lower contact, and a second closed position wherein the first upper contact continues to engage the first lower contact and wherein the second upper contact engages the second lower contact.
In yet another aspect of the present invention, the multiple contact fluid pressure switch includes a central lower contact and a first outer lower contact spaced from the central lower contact. Moreover, the upper contact is a common upper contact that is affixed to the diaphragm above the central lower contact and the first outer lower contact. In this aspect, the switch further includes a second outer lower contact placed below the common upper contact. The switch is movable between an open position wherein the common upper contact does not engage the lower contacts, a first closed position wherein the common upper contact engages the central lower contact, and a second closed position wherein the common upper contact continues to engage the central lower contact and wherein the common upper contact engages at least one of the outer lower contacts.
In still another aspect of the present invention, the multiple contact fluid pressure switch includes a central lower contact and an outer lower contact spaced from the central lower contact and surrounding the central lower contact. The upper contact is a common upper contact that is affixed to the diaphragm above the central lower contact and the outer lower contact. In this aspect, the multiple contact fluid pressure switch is movable between an open position wherein the common upper contact does not engage the lower contacts, a first closed position wherein the common upper contact engages the central lower contact, and a second closed position wherein the common upper contact continues to engage the central lower contact and wherein the common upper contact engages at least a portion of the outer lower contact.
In yet still another aspect of the present invention, a fluid pressure switch includes a cavity. Two lower contacts are disposed within the cavity. A diaphragm encloses the cavity. An upper contact is disposed on the diaphragm above the lower contacts. In this aspect, the fluid pressure switch is movable between an open position wherein the upper contact does not engage the lower contacts, a first closed position wherein the upper contact engages one lower contact, and a second closed position wherein the upper contact engages both lower contacts.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: